This invention relates generally to a backflow preventer which may be used in conjunction with a dispensing device such as a proportioner that mixes liquid detergent with water to provide a diluent mix.
Backflow prevention devices are used to prevent return of contaminated liquid mixes from dispensing devices, such as proportioners, back into a clean water supply.
A backflow preventer of the type under consideration is disclosed in U.S. Pat. No. 3,171,423. This patent discloses a combination diaphragm and check valve disc. These two components are both required to cooperate to provide backflow prevention. The check valve disc tends to impede flow into the outlet of the backflow preventer rather than allow a smooth flow into the outlet during normal operation.
Fluid mixing devices, sometimes know as proportioners typically make use of the venturi principle for inducing the liquid detergent into the water stream and backflow is prevented by providing an anti-syphoning air gap upstream of the venturi. This arrangement may function effectively in preventing backflow but may result in the discharge and overspill of the water through the air gap between the venturi nozzle and the inlet nozzle, which drips down the side of the proportioner.
U.S. Pat. No. 5,253,677 is an example of an air gap system which provides barriers adjacent to the windows which provide the air gap to prevent overspill. Unfortunately, the barriers block a clear view through the air gap which is required by some government authorities. Finally, U.S. Pat. No. 5,797,420, also owned by the assignee of the present invention, provides a unique structure for the venturi nozzle to avoid overspill while permitting a clear view through the air gap. This proportioner works well for its intended purpose to avoid overspill and provide backflow prevention but requires a special venturi arrangement.
The present backflow preventer solves these and other problems in a manner not disclosed in the known prior art.
This backflow preventer avoids the problem of backflow contaminating liquid detergent into the water supply, yet substantially precludes the escape of the liquid to atmosphere during normal operation and further permits smooth liquid flow to the outlet of the backflow preventer.
This backflow preventer comprises an upper body portion having an inlet and a lower body portion having an outlet. Means for preventing backflow is disposed in the body including a nozzle communicating with the inlet, a passage communicating with the outlet and a diaphragm disposed between the nozzle and the passage to control flow into the passage. The diaphragm is movable under water flow from a closed position blocking flow into the passage to an open position permitting flow into the passage; and is closed by reverse back-up flow.
It is an aspect of this invention to provide that the backflow preventer means includes resilient means for moving the diaphragm into the closed position.
It is another aspect of this invention to provide that the nozzle includes a depending hub portion; and the diaphragm includes a sleeve portion overfitting the hub portion in the closed position.
Yet another aspect of this invention is to provide that the nozzle includes an outer ring portion an inner hub portion and an intermediate perforated web; and the diaphragm includes an outer ring portion between the body and the nozzle and an imperforate web.
Still another aspect of this invention is to provide that the passage is formed by a tubular stem having an upper end spaced from the diaphragm sleeve in the closed position and an upper passage portion receiving the sleeve in sealed relation in the open position.
It is an aspect of this invention to provide that the tubular stem includes outer support means and the sleeve includes engagable means; and spring means is disposed between the support means and the engagable means tending to move the diaphragm into the closed position.
It is another aspect of this invention to provide that the body includes a side passage extending through the body.
It is still another aspect of this invention to provide that the body includes opposed side passages communicating with ambience.
It is an aspect of this invention to provide that the diaphragm sleeve includes a lower end spaced from the upper end of the tubular stem when the sleeve is in the closed position to provide an exit for reverse flow.
It is yet another aspect of this invention to provide that the tubular stem includes an outer support means and the diaphragm includes a recess between the sleeve and web; and the backflow preventer means includes a spring having a lower portion operatively seating on the tubular outer support means and an upper portion received by the diaphragm recess and exerting a force on the diaphragm tending to move the diaphragm into the closed position.
It is an aspect of this invention to provide that the spring includes an annular retainer receiving the spring upper end and being engagable with the diaphragm.
It is another aspect of this invention to provide that the body upper portion includes an inner support portion and an inclined support portion below the inner support portion; and the diaphragm includes an outer portion supported by the inner support portion and an intermediate web which is permitted to move downwardly by the inclined support portion when the diaphragm is moved into the open position.
Another aspect of this invention is to provide that the passage is formed by a tubular stem having an upper end spaced from the nozzle and an upper passage portion receiving the sleeve portion of the diaphragm when the diaphragm moves to the open position, the stem upper end being configurated to facilitate receiving said sleeve portion.
It is an aspect of this invention to provide that the gap assembly includes O-ring receivable in the inlet of the body to retain the nozzle and the diaphragm in place.
This invention provides a backflow preventer which utilizes a simple and inexpensive arrangement of parts and is very efficient for its intended purpose.